Note that, although the attack site can inject its own content, it cannot change the URL appearing in the Location Bar. Firefox and Mozilla have the ability to deny access to the Location Bar so all pop-up windows always have it. To turn on this feature:

1. Enter about:config in the Location Bar.
2. Enter dom.disable_window_open_feature.location in the filter field.
3. Right-click (Ctrl+click on Mac OS) the preference option and choose Toggle (the value should change to true).